I have been growing and studying the finger lime for many years. I do not believe it would produce a 'sport' of this form. However, it does hybridize very easily with other citrus and this shape of fruit is the one you would expect with such a cross. Without genetic analysis it is very difficult to say which citrus variety is the other parent.

I have a picture of the giant lime cut opened. I need to find it first on my computer. I won't be able to compare two different varieties though. I don't have the regular finger lime fruit yet.

Here are some pics. The limes get yellow if left on the tree longer.

Thanks for the pictures. It looks kind of disapointing for anybody looking for a proper finger lime with caviar like fruit. There is a local grocery store with an attached greenhouse that sells plants during the sumer months. They have giant finger lime plants right now but i think im gonna pass on them.